[Elly]

Meganium @ Leftovers
Ability: Overgrow
Nature: Bold(Calm)
EVs: 252 HP / 184 Def(SpDef) / 72 SpAtk
- Energy Ball
- Aromatherapy
- Reflect(Light Screen)
- Grasswhistle/Leech Seed/Synthesis

Basic team supporter. Energy ball is your only attacking option, and leaves you walled by Grass-types, but it is still your best option. Aromatherapy clears any status problems you mind find yourself with. The last attack slot is really a toss up based on your preference; status, self-healing, or team healing. The options in parenthesis should be used together, not mix and match. Calm, Light Screen, and the SpDef EVs make a a special wall, while the alternates make a physical wall.

Originally Posted by WildAce

Meganium @ Light Clay / Leftovers
Ability: Overgrow
Nature: Careful
Evs: 252 HP / 128 DEF / 128 Sp.DEF
- Reflect
- Light Screen
- Leech Seed
- Body Slam

Pardon the EV spread.
Sadly, it gets walled by Ghosts easilly (save Leech Seed + LS).
This works best with SR and/or Spikes, of course.